Core D: Biostatistics - The Biostatistics Core consists of personnel with expertise in statistics and clinical informatics, including Drs T Johnson, P Schoenfeld, and B Athey. The goal of this Core is to collaborate with NTR investigators and other network scientists to enhance the rigor, quality, and safety of the research data. The Core personnel have been chosen because of their expertise in biostatistics and informatics, and their knowledge of gastrointestinal cancer screening. Biostatistics core personnel will collaborate with investigators in the Primary and Task Specific projects, and will work with the other Cores to provide support in all stages of the research, beginning with the formulation of the research question, and continuing through experimental design, data collection, storage, and archival, data analysis and interpretation, and writing of manuscripts.